A reaction composition containing a urethane acrylate can be made to have excellent characteristics of toughness, flexibility, scratch resistance, weather resistance, chemical resistance, and the like. Further, the composition has a characteristic of curing within a short period of time through heating or active energy ray irradiation, and is favorable for production of components for optical use, resist compositions, hard coat compositions, and ink compositions for inkjet.
In these latter days, in mobile electronic appliances such as notebook-size personal computers and mobile telephones, components having a fine patterned indented surface (for example, a key sheet) formed of a reactive resin composition on a sheet-like transparent plastic substrate, and housings with high-quality design are used in some cases and high pencil hardness and scratch resistance are required therefor. Consequently, attention has become paid to reactive compositions containing a urethane acrylate.
The cured product using the reactive composition described in Patent Literature 1 is excellent in scratch resistance, but in fact, the composition contains a solvent as described in Examples therein, and is therefore unfavorable for use in shaping applications. On the other hand, the cured product using the reactive composition described in Patent Literature 2 is disclosed to have excellent transparency and scratch resistance, but the composition uses a polyfunctional (meth)acryloyl group-containing compound such as 1,6-hexanediol diacrylate, trimethylolpropane triacrylate or dipentaerythritol hexaacrylate, and therefore, it is desired to reduce a curing shrinkage, to prevent an occurrence of a crack of the cured product and to improve an adhesiveness of the cured product to a substrate.
In Patent Literature 3, there is seen a description relating to a composition in which a urethane compound of a hexamethylene diisocyanate trimer with a monofunctional alcohol such as HEA, HPA, or HBA and a urethane compound with pentaerythritol triacrylate are produced, and thereto are incorporated a polyfunctional (meth)acrylate such as dipentaerythritol hexaacrylate, caprolactone-modified dipentaerythritol hexaacrylate, or dipentaerythritol-EO 12 mol adduct hexaacrylate. However, urethane acrylate as a base has high viscosity, and in order to prevent the physical properties from worsening, the composition naturally contains a polyfunctional alcohol derivative having high crystallinity and high viscosity. Therefore, there remain some problems in that a degree of lowering viscosity is low, and in case a monofunctional diluting monomer is added for lowering the viscosity, the physical properties of the cured product greatly worsen. Though the material is for shaping on a film, there is not made any evaluation in curing the composition on a film, relating to film deformation such as curling behavior, or curing shrinkage of the resin.
Not limited to the above-mentioned patent literatures, in a (meth)acrylate of a polyfunctional alcohol such as typically glycerin, diglycerin, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, tris(2-hydroxyethyl) isocyanurate, or sorbitol, an urethane acrylate compound reacted with an isocyanate with intentionally making a hydroxyl group remaining therein is incorporated in some cases in order to make a reactive composition to have high pencil hardness, scratch resistance, abrasion resistance, adhesiveness to substrate, transparency and weather resistance, which the present invention intend to have. However, as a whole, these urethane acrylate compounds have a high viscosity, and therefore have a problem of adhesiveness reduction owing to curing shrinkage and the same problems as in Patent Literature 3.